How to gain muscles for skinny guy?

Hello, Im 16 years old and im 6ft3 tall and i weight 70 kg. Im typical ectomorph guy :/. I don't get bullied about my size because I still can win "big" guys in a fight. Girls still seems to like me because im good looking but i want to gain weight to boost my self confidence. How can i gain muscle mass and what kind of diets i should follow? P.S i play ice hockey :D Thanks